The invention relates to the field of electrical circuit breakers; and in particular to multi-pole circuit breakers having fault current limiting capabilities.
In the design of circuit breakers of this type, compromises are required between various goals. The breaker should be compact, fast operating, have accurate and repeatable trip levels, and high current interruption capability. To accomplish all these goals, mechanisms have been made which become increasingly complex, and may include many relatively long fingers and levers.
U.S. Pat. No. 4,276,526 discloses a miniature circuit breaker which has a normal contact opening mode using spring force, and a fast opening mode using a solenoid first to unlatch the contact mechanism, and then to force the contacts apart. The resulting mechanism is quite complex.
U.S. Pat. No. 4,636,760 discloses a breaker mechanism which allows remote operation by one solenoid, thermal tripping, and magnetic tripping by another solenoid. As a result this mechanism is also complex, with a number of long elements required for operation.